In a new study, researchers tested more than 250,000 women and found that oral contraceptive use protects against ovarian and endometrial cancer.
The protective effect remains for several decades after discontinuing the use.
The research was conducted by a team from Uppsala University.
Ovarian and endometrial cancer are among the most common gynecological cancers, with a lifetime risk of just over 2%.
Endometrial cancer is slightly more common but as it has clearer symptoms and is therefore often detected at an early stage, the mortality rate is low.
However, ovarian cancer is among the deadliest cancers, since it is often not detected until it has already spread to other parts of the body.
The first oral contraceptive pill was approved already in the 1960s, and 80% of all women in Western Europe have used oral contraceptives at some point in their life.
Oral contraceptives include estrogen and progestin, which are synthetic forms of female sex hormones.
The estrogen and progestin in oral contraceptives prevent ovulation and thereby protect against pregnancy.
In the study, the scientists compared the incidence of breast, ovarian, and endometrial cancers between women that had used oral contraceptive pills and never users.
They found that women who had used oral contraceptive pills had a much lower risk of developing both ovarian and endometrial cancer.
Fifteen years after discontinuing oral contraceptives, the risk was about 50% lower.
However, a decreased risk was still detected up to 30-35 years after discontinuation.
However, oral contraceptive pills have previously been associated with an increased risk of breast cancer.
The team only found a small increased risk of breast cancer among oral contraceptive users, and the increased risk disappeared within a few years after discontinuation.
The results suggest that the lifetime risk of breast cancer might not differ between ever and never users, even if there is an increased short-term risk.
The results from the current study are important, since oral contraceptive use has commonly been linked to side effects such as deep vein thrombosis and breast cancer.
One author of the study is Åsa Johansson at the Department of Immunology, Genetics, and Pathology.
The study is published in Cancer Research.
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